Telephone system.



E. H. CLARK.

TELEPHONE SYSTEM.

APPLICATION FILED JULY 3, 1912 1,127,405. Patented Feb. 9, 1915.

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Patented Feb. 9, 1915 ESEEETSSHBET 2.

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TELEPHONE SYSTEM. APPLICATION FILED JULY 3, 1912.

Pa-tented Feb. 9, 1 15.

Azy s E. H. CLARK:

TELEPHONE SYSTEM.

APPLICATION FILED JULY3,'1912.

Patented Feb. 9, 1915.

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B.H.GLARK. TELEPHONE SYSTEM.

APPLICATION FILED JULY 3, 2912.

1,127,405. I Patented Feb. 9, 1915.

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nnncrnrc coherent-r, new roan, it. a corroaarron rnrlurnonr; i i I i t Patented Feb. 9, Helen Application filed. July 3, 1912. Serial no. torre;

.fl all evhom it may concern f the it known that L Essen H. CLARK, a citizen of the Qnrted States of America, and

-41 .4a resident or Austin, county of Cook, and

Estate oflllinois have invented a new and useful Improvement in Telephone Systems,

17.. at which the following is a specification.

19 ".It relates particularly to telephone syslflyjuvention pertains to telephone systems and its ultimate obgect 18 the economy ofhne conductors;

items wherein one or more main or central ofiices-are supplemented by one or more outoifices or sub-ofiices, in which groups yet, subscribers lines center and between w huh and the central otlice or offices trunk ,iines e tend;

I -have chosenparticularly to illustrate my invention as applied to a telephone system employingmanually operated switchboards at its main switching center or centers, but, obviously, it may be applied to other than manual systems;

in its broad aspect my invention contem plates the bringing ofthe subscribers lines from small outlying communities of subf these community centers, or sub-centers,

scribers to convenient centers remote from the central office or o'flices instead of carryin'g themto the respective central oliices where they are to be switched. From each as they may be called, I extend a group of lines, fewer in number than the subscribers 7 lines, to the respective central ofiice. At the central 'oflice I provide the ordinary switching mechanisms, either automatic or manual, capable of operating substantially in the same manner as if all the lines had been brought .to' the central ofiice rather. than to the sub-ollices at the sub centers. The central office equipment is provided with the full number of jacks or other connection terminals that it would have if allthe lines extended to the central cities, but instead of these connection terminals being extended by paths permanently connected to the corre sponding lines, they terminated in what I may term blind paths, each physically dissociated from its correspond mg line, although permanently associated Q therewith, as by number or other designa tion. "Likewisa'each or the subscribers lines entering a p 7 of which is,

sub-oliice terminates in blindsponding switchboard terminal at the central oifice, its only association. being thlat of mras reruns: oration By my invention the physical connection between the blind lead of a subscribers' line at the sub-or fice and that of its corresponding switchboard terminal at the main ollice is supplied automatically, upon the initiation' a connection at either end, by any oneof of a group of trunk lines extending between the sub-office and the main ofliceythe' number of trunks in such "a group always being smaller than the number of subscribers lines have described such a'system in my application for a telephine system; Serial. No. 411,669, filed JanuaryQO, 190 8, and'the system of my present j application is an improvement thereon. In that application the specific circuits and apparatus described required that each trunk line between the main office and the sub-office consist of three can: ductors. While such an arrangement re-. sultedin a very large economy in wire, yet it is greatly to be desired that trunks conform more nearly with standard practice to the extent of being two conductor rather than three conductor trunks. Such requirement is met by the apparatus and circuits which I describe herein Other advantages over the system of my prior application are also to be found,.such, for instance, as the originating at the subscribers station; Fig.

. .-'3l 1S: "modification of the arrangement shown in 5 use diagram of suothe group is intended to serve, thus resultmg in the desired economy of 'line' v'vires. I I

scribers line, the 'central 'ofiice, outgoing trunk line and 'sub-oflice circuits employed for completing acall to a subscribers' station; Fig. 6 is a circuit diagram of a standardmanual switchboard cord circuit adaptable for use with my invention; Fig. 7' is'a simplified circuit diagram, showing the ar- 'ra-ngement for associating the trunk lines which they serve. g

The automatic switch which I have'shown with the subscribers lines of the group' in Figs. 1 and2is of atype. common; in theart and will be easily understood from the drawing, It is one in which a plurality of wipers 1, 2, 3, 4 and 5, rigidly mounted 'upon "a, shaft 6, journaled in housing 7, may be made to move in a circular path each-overs} row of contacts 21, 22, 23, 24 and-.25; Rof tary movement in a clockwise direction is impartedto" these wipers through "the ratchet wheel '8', impelled by pawl-9,1andoperated in anobvious manner by theelectroma'gnet 10, which may becalled the step-- ping magnet. The reverseor countencloc wise movement of the wipers isproduced by the coil spring 11,,-fixed at its inner end to thehousing 7 and at its'outer end tothe ratchet wheel a 8; This counter clockwise movement or release is permitted by the- 'energi'zation of-themagnet 12, wh'ich with- 1 draws the holding pawl 13' from engagement-wi'ththe teeth on Wheel-SLjL-The magnet;

sets of contact springs, one of which is controlled by the stepping magnet '10; another of which is controlled by the release magnet 12,,and the'third'of which is controlled by the rotary position ofv the ratchet wheelSL The-springs of the group controlled by the magnet 10 are designated 14, 15, 16 and- 17 on the drawing, and these are so arranged that each attraction of the armature of the stepping'magnetwill bring all of the fourv springs into contact with each other, each release of. the armature likewise causing.

their separation. For purpose of greater clearne s s, the amount 0 separation of the springs, 14 to 17 inclusive, each from the other,- is exaggerated on Fig: .1 of the drawings, but in {practice they' should" be so d'i'sa posedwith reference to the moving 'parts' associated with the-stepping magnet 10 that these 's rings will all-be closed during'that part o the movement of the armature which takesnplace -before the wheel 8 has been moved sufiicientlyztogcause the making and 'breaking among the third setof springs, 31'

to 40, inclusive, which set, as stated, is con trolled by the'jrotaryposition of the ratchet The}; Jin'gs of-theqgroup' under thecon- "'ffggreleasemagnet121 ave desigb326,,2 7, 28, 29 -'a nd 3 0. 'Qf these, 29 are" normally inengag'ement, but are :31, 34, 37"and, 39 of this group chan their gspective' ;rows,fand by' elf-normal posit n mean any otherqposition, this use normal and othnormal-t being one tha 12 maybe called the release magnet. -Associated with the switch mechanism are three connected by the usual metallic circu 'matic switch contacts which COJIflj'Jl other sets of contacts are simihurly eon relay49, and a line signal 35, 36, 37,38,39 and 40, former; wh fil' term the off-normal switch, and is contra an-obvious manner by the pin 41, n on'lth'e. ratchet wheel 8. Tl'l8lIlOV8iJlf} ed in relation withr'espect to the others when the fwipers a zjid; ratchet wheel move from m to anbfimormalposition, or vice a. By'nen'nal.v itiqn of the wipers l .t tan that positioirfin; whichv the wipers 1, :13, {1", 4. andlfi rest on thefirst-contactsof their :re-

the

Ijully "understood in the auto maticsw-itching'art. v

' Ivvhave not"illustratedmy switch in extremedetail, as; do not desire to be limited to any particular form of switch. A large variety of switches, capable of being ri'xadjly' adapted .to operate in connection with my system, the'art.

are available and well known in will first describe the circuit employed for connectin a calling subscribers ii 1 to ats correspon mg switchboard terinimi at the main office upon the originatioi': 03% a call'b the subscriber on that line. In lfig.

3, I s ow in the lowcj right hand cor. common battery subscriber-s equipnmm composed of the limbs a3 and 1-41:, w line apparatus at the sub-ofii'cc- Th the terminals of the subscribers line are sin W11 diagrammatically immediately above line apparatus. is shown, but it is to be understood tl ed to subscribers lines- The subsc" lines are multiplied through the contac the otherswitchesot the group in a manner to-be'hereinafter described. The a irnn-atns associated with the sub-oilice end. of the trunk l1ne is shown 1n the lower right hand portion of the samedrawmg, tins a iiparatus being connected to that at the main ollicc' by the trunk conductors 45 and .l in paratus associated. with the main end of the trunk line is shown in the upper. 'righthand-portion, and in the um m hilt handportion is shown the main oflice connection terminals of the subscribers" lines,

.-.'1-he connection terminal for this partir lnr line is inthe form of aspiring jack Ll-'7,

ith which is associated acut-ofl' relay 1 53,

50. It inusgt he re Only one subscribefis 7 l 2 ti member-ed that normally there is no physical connection betv-zeen the line of subscriber lz2 andhis jack 1:? at the distant main oliice, and that the object of the automatic switching apparatus shown is to sup 'ply the gap in this subscribe1"s line between the sub-office and. the main ofiice as soon as the subscriber originates a callby rcmov ing hisreceiver from its hook. The opera tion to this end is as follows: T11e subscriber desiring a connection removes his receiver from its hook, and thus energizes the line relay 51 over the metallic circuit of his line. The operation of this relay places a ground upon the starting wire'52, which ground remains until the action of the cutoil relay at the somewhat later time. At

this point it may be saidthat the line and cut-oil relays 51 and 53are individual to the subscribers line and that the starting wire is individual to a switch. but is common to ausmall group. such as ten of these subscribers lines with their corresponding lines and cut-oil relays.. The branches from the wire 52 represent the wires to the back contacts of each of the cut-oh relays 53 belonging to the group of lines servedby that wire. The grounding of the starting wire 52 permits current to pass through the stepping magnet 10 of the rotary switch. this current being periodically ln'oken by a constantly running interrupter 54-, capable of producing impulses'at the required frequency for the proper operation of 'the switches. An impulse through the stepping magnet 10 causes the closure together of the contacts ll, 15, 1G and 17. as already describedin connection with Fig. 1, and the contacts 15, 16 and 17 are thereby grounded through the contact 14.-

As the first or initial operation of the stepping magnet 10 produces many changes in the circuit conditions, and as these changed conditions maintain until the switch contacts of the calling line are reached by the wipers. the circuits and apu .ratus.wil] be described, first, for the initial operation of magnet 10 and then for the second and succeeding operations. The initial. grounding of the contact 15 produces a circuit which, through the'contacts 33 and 34 of the oft-normal switch, causesthe operationv ot'the trunk cutotf relay 18. The operation of relay 18 disconnects all apparatus from the line wipers 1 and 2, thereby 'preventing disturbance on the contacts of the subscribers line over which'these wi )ers pass during the subsequent operations 0 the steppingmagnet 10. The operation of re lay-1S also disconnects the'ground connection from busy test wiper 5, and disconnects the continuation of the starting wire 52 to prevent the starting of another trunk switch of the group, as willbe hereinafter described. The grounding of contact 16 energizes relay ]S'..\\'hi-h. through its right hand contacts. switches the controi of the stepping magnet ll) from the starting wire to the testing wiper 4. it 2 iso provides an alternative path through its Ielt hand contacts for continuing the energization of re lay 18. after the initial operating circuit for this relay has been broken at the contacts of the nit-normal switch.

The grmmding of the contact 17 of the stepping magnet 10 causes. through conductor l5 of the trunk and contacts 36 and 37 of theoit-normal switch. the initial 01101; gization of stepping magnet 10 at the central otlice end of the trunk. The initial operation of the stepping magnet 10 causes, through its contacts 14- and 15, the operation of the trunk cut-oil relay 18 The operation of this relay disconnects the line wipers 1 and 2 from the rest of the apparatus, for the purpose heretofore described, and places battery through the resistance .35 on the trunk conductor 4-6 for the purpose of energizing the trunk release relay 20, when its circuit is completed at the sub-otiice. This relay also switches the control of stepping magnet 10 from contacts 36 and 37 through which the initial impulse was received, directly to the trunk line conductor The relay 18 also, through its left hand contacts. dissociates the release relay 20 and the release magnet 12 from their respective wipers 3 and t.

It will be remembered that in the description of the operation of the switch in connection with Figs. 1 and 2, the contacts of the stepping magnet were closed in advance of the changing of the relation of the contacts of theoff-normal switch.

It will be noted from the description of the circuits and apparatus given above, that alternative circuits to those originally passing through the oft-normal switches have been provided for the subsequent operatiini's of the apparatus. The relays 19 and L? are made of the slow-acting type by the presence of a mass of copper associated with their windings, or by any of the other well known methods, so that they will not become deen'ergize'd between, the successive recurring impulses. supplied'to them through the action of the stepping magnets lOand 10, respectively. This arrangement insures that the circuits, as described abo\'e,'be maintained throughout the subsequent operations of the stepping magnets 10 and 10 or until the wipers 1, 2-, 3, t and 5 and 1 2 ,3 and 4 rest on the sub-oiii'ce terminal switch contacts and the main office terminal switch contacts, respectively, of the line of station 42.

Innnediately following the attraction of the armature of the stepping magnets and the subsequent moving of the Wipers from their normal positions, the relation of the] contacts of. the ofl"-normal switches is Changed (Jpntacts 31 and 32 are closed,

thereby completing the circuit from the release relay to the contacts of the supervisory relay 56. and causing relay 20 to be operated. Contacts 33 and 34, which, provide for theinitial energization of relay 18, arebroken and contact 34 is connected to contact 35, thus providing an alternative path for the operation of the relay 18, for the, purpose to be hereinafter described. The starting wire 52 is disconnected from the stepping magnet 10 at the contacts 36 and 37 an will event y continue this wire to another trun'l'r. switch for the purpose of enabling'other lines normally served by this trunk to'originate calls.

A The circuit between the release magnet 12 and contacts of relay 20 is completed through the contacts 39 and 40, thus pro viding a path for the operation of this magnet when the trunk release relay 20 is deener-gized. The breaking of the connection between. the contacts 36 and 37 of the ofl-normalswitch at the central office end of the trunkl broke the initial starting circuit of the stepping magnet 10, this magnet having been-provided with an alternative path, as previously described. "The closure of contacts 34 and places ground upon the right hand armature of the release relay 20 this being for the purpose of later ,providing a locking circuit for relay 20 Contacts 31 and 32 complete a circuit to the release. magnet 12 which provides means for subsequently releasing the switch at the proper time.

In the circuits, as described. above, provision has been made for the continued operations of the stepping magnet 10, and the simultaneous operations of the stepping magnet 10*, as the wiper 4 passes over the contacts 24 24 etc., of thelines associated with this switch. Through the operation of the off-normal switches, preliminary circuits have been established for the, sub- 'sequent release of the apparatuswhen a connection is no longer desired.

As has been previously describechthe controlcircuit for the stepping mlgnet 10, after the initial operation of this magnet, is con-- nected to wiper 4. It will be noted that as long as the wiper 4 encounters a groundv connection on the contacts 24 24 etc., over which it passes, acircuit will be provided for the operation of magnet '10. The contacts 24 24 etc., will be grounded in all cases except that of the line on which the receiver is removed from the hook switch and which has not as yet been connected with its respeet-ive centrzd ofhce terminal; or, in other;

words, ground will appear upon these con;

is connected to a circuit which.

on all lines which are idle, or which are actually engaged in a connection. Therefore, assuming station 42 to be calling, when the wipers of the switch are stepped to contacts 21 22 23 ,24 and 25 ground will be encountered on contact 24 and the switch wipers will be moved to the next position, or that of the line which we have assumed. as desiring to originate a call. On this line the contact 24 will be disconnected from the ground, inasmuch as the removal of the hook switch at the station 42 caused the energize.- tion of the relay 51, and as cut-off relay 53 has not as yet been energized, relay 51 is still in an energized condition. As previously described stepping magnet 10 is made to operate simultaneously with the operation of stepping magnet 10. Therefore, the wipers of the central ol'lice end of this trunk line will have been moved to the contacts 71 72 73 and 74 or the central oilice terminals of the line 42. The stepping magnet 10 will now cease to be energized and the slow-acting relays 18 and 19, which have been maintaining the circuit conditions since the initial impulse, will also become deenergizcd. The deenergization of relay 19 will, through its left hand contacts and the contacts of the release relay 20, which relay has prtwiously been energized, establish a circuit through the wiper 3 for the operation of the cut-Ofi' relay 53, thereby disabling the line relay 51 and establishing ground on the contacts 24 of the other switches through which this line is multiplied. These same contacts of relay 19 also establish a preliminary circuit for the subsequent release of the switch. The deenergization of relay 18 connects the contacts 21 and 22 of the line of station 4-2, through the wipers 1 and 2, with the repeating coil and supervisory relay, thereby producing a circuit over which conversation may take place and over which supervisory signals may be passed. The release of relay 18 also places ground, through the-trunk conductors 45 and 46 to the contajcts 71 and 72 respectively, which contacts are the c'entral oflice terminals associated with station 42'. The closure of the left hand contacts of this relay has established the preliminary circuit for the release.

The complete circuit involved in the subs'cribers line is asfollows: from' ground,

through winding of relay 56, repeating coil (38, contacts of relay 18, wiper 1, switch contact 21 conductor 43, through station42,

ated, produce a locking circuit which contlnu the cincrgization this magnet until the switch wipers rest on their normal contacts. Relay 18 is operated. through a circuit established by the left hand contacts of relay The operation of relay 1% disconnects the wipers-l and from, the rest of the amiaratus, and thcrcl'iy permits them to pass over the swit .3 co; t withoutintcrfering with the lines connect id thereto. It will be l'Qllflilll'l bw. i that a battery connection has been ll rained. with trunk line conductor M3 for f .e Pllllfulifi of energizing trunk rc so i 20. flie operation of relay i13 places liiatl y. tl'nt'ough a resistance on the shore mentioned twink conductor. thus causing relay E0 to continue in operated position until the relay released. when the switch with which it associated reaches its normal position. ll hen relay 20 is dcenergined, a circuit is established. for the operation of magnet This magnet is ol' the locking type as oo/tore described. and after having once been energized. re mains in an. eucr 'iracd position until the wipers oi this switch rest in their normal position. llclay also operates cut oli' rc lay 18 for the purpose of isolating the line wipers of the sw' h during ieir return to normal p0 ion. Tho main ollice and subollice terminals of the su ibe -s lines have now linen physically lated and the trunk line and. associatcrl apparatus is in its no mal posit on.

In if or to pi. rent a trunk line and its associated appar is in liecouiing 'iuop cratiro. due to the start up" of a switch by a momentary ground on conductor ll or by an accidental nioicincnt of the armature of rclay 51 or magnet .10, provision is made for automatically releasing: the switches when the wipers have passed over the switch conhuts and have failed to find, a line calling. This automatic release is provided for by the row oi. contacts 717. 7:2 753". Tl. placed inin'icdiatoly beyond the last lino contacts of the switch. The lower two contacts of the groups 75. and 7 1- are connected to ground. iind when the wip 3 and 1- re contact a release circuit es ablished similar to that heretofore dc I will now if scribe the circuit and apparatus cnipl ycd in connecting a switchboard terminal at thinain oflicc with it corresponding subsci' s line and t. ml at the sub ollicetlns circuit being the one our ploycd in rmupletin jq the connection with a called. sul hur s line.

The oruu'alor. al ar haying learned the number of the subscriber to he called, tests a niulti jilc if of that line in the usual manner to determine whether or not the subscriher s line is already connected with at some other point n tliu multiple. l? the multiple associates jh the line is found st on this argo-rs idle, the operator inserts the calling plug of a cord pair in the multiple switchboard jack and rings the subscriber in the usual man nor. The act of inserting the plug of the cord pair in the multiple jack causes thd thereby provide a busy back signal for theoperator. The circuits employed in the selection of the outgoing trunk and its associated switches and: the connection with the subscribefis line at the sub-office are as follows: The insertion of the plug in the multiple jack causes the relay 61 Fig. 5),-associated with that line, to be energized by a *ircuit as follows: from battery associated i'rith the cord circuit (Fig. ll to relay 59 contactsof key at. sleeve of plug 57 sleeve of jack 63 (Fig. 5). winding of relay '6'1, thence to ground The operation of relay ill places ound on the common starting truuli' to s! h. find and connect with. the switch terminals of that line at tbe lnain oliicc. and simultaneously cause the switch at the sub-cilia? and of the trunk to connect with the switch. terminals of the corresponding line. The circuit established for th purpose oli giving'the initial or starting ini pulse to the stepping magnet of the trunk switch is as follows: from ground to contacts of relay 61. contacts of relay 62. starting wire contacts 37 36 of the oil-n01 nial switch. winding of stepping ma gnct 10 thence to and through the interrupter 54 to battery. This circuit includes the winding of relay 10 and will cause it to be energized.

its the first or initial operation of the stepping magnet 10 produces many changes in the circuit conditions. and as these changed conditions maintain until. the switch contacts of the calling line are reachedv by the wipers. the circuits and apparatuswill be described. first. for the initial operation of the magnet 10 and then .for the second and succeeding operations.

The initial grounding of the contact 15 produces a circuit which. through the contacts 33" and of the oil-normal swltoh.

'causes the operation of the trunk cutoff reductor' it, to replace the battery connection which, up to this time, was suppliedthrough the continuation of the starting- Wire 52: to prevent the starting of another tmn'hsw tch The grounding'of contact 16 energizes relay 19 which, by meansof one of its lower set of'conta-cts and contacts of the ofi-norrnalswitch, switches the control vof the stepping I,

magnet lo i'ronl the starting Wire to the the cord circuit. Relay l8 also disconnects of-a group, as will'vhe hereinafter described,- 1

testing Wiper 4 It also providesan alternative path through its upper set of, con

tacts for continuing the energization of relay 18 after the initial operating circuit for this relay has been broken at the contacts of the off-normal switch. The grounding of contact 17 of stepping magnet 10 senses, through trunk conductor. 45* and contacts ".37 and 36 of the ofi normal-switoh, the initial energization of the stepping magnet 10 at thesub-ofiice end or" the tru nln The initial operation oithe stepping 16 3 causes. through its contacts 14* and. 15. the operation of the trunk cutofi relay 18 The operation of this-relay disconnects the line'wipers 1 and 2 from the restofthe apparatus for the purpose heretofore'described, and switches the control" of the stepping. magnet 10 from contacts 36 and 87 of the off-normal switch, throughwhich the initial impulse was received,.- tocontacts nf relay 6?, and thence to the-trunk l ne conductor 4:5 This relay. also provides acircuit, for continuing the energization of relay 67. li lagnet 10 through contacts 14 I and" 17 provides ailpath for the initial energizethrough the winding of the repeating coil tion of the relay 67. This relay is connected .reloasamagnot 12 and contacts of relay l thus providing apath forthe ope 20 1s denergi'zed.

their normal positions, the relation of the contacts of the "oil-normal switches is changed.- ,;Contacts 33 and 34 are ihrolz the circuit of relay 18", which origin passed 'through these contacts, having transferred to contacts of relay 1% starting wire 52 is disconnected-from stepping.n agnetl0 at the contacts 36* ans 37 and'is connected through contacts t and 38 to 'a circuit which will-eventual continue this wire to another switch for the purposeoi' enabling other lines, normally seryed by this trunk, to originate calls The circuit between the release magn and contacts of the relay 19 is cont through the contact-539 and 10 th riding apath for the operation of this net 1 when disconnection is desired.

breaking of the cohnection hetwe' n taots 36 and 37 of the oE-normal sw ch at the suh-oilice endofthe trunk hrolts the initial controlling circuit of the step magnetiti this magnet having been sided with an alternativepath, as previ ously described; The circuit between t e is completed through'the contacts 39 of this magnet when the trunkrclease a I a 0 In the c1rcu1ts as described above, provision hasbeen made for the continued opera- .tion of the stepping rnagnet 10 and the simultaneous operation of the stepping magnet 10 as the wiper, i passes over the contacts 88 88 "88 etc, of-the' lines as- 68 to the trunk conductor 4:6 whichhascircuits to those originally passing through the offmormal switches have been provided for the subsequent operations of the apparatusi The relays 18 and 19 at the central oiiice and 18 andQQ? at the sub-ofiice are made of the slowacting typaso that they wili not hecomeldeenergized during the subsequent momentary breaking of their controlling" circuits,

immediately following the attraction of thearmatures-of the stepping magnets and so thesnhsequent moving of the wipers trom' sociatechwiththis switch. Through the operation of the od -normal switches, preliminary circuits have been established for the subsequent release. of the apparatus when a connection is no longer desired.

As has been previously described, the icontrol circuit of the stepping magnet lO by the initial operation of this magnet is connected to wiper 4 it will benoted'that as long as wiper/i encounters a ground con- Election on thevarious contacts 88 88?, etc, over which it passes, a circuit will be provided for the operation of magnet 10 The contacts 88 88 etc, will be connected to; ground in all cases except that of the line or" which a-plug has been inserted the multiplejack, and which has not as yet been connected its respectivesuhscrihers line, or, in other words, ground will appear upon those contacts of all the lines on it will he noted that the contact 88 is conneeted directly toground, thereby. insuring that the wipers will always p ss over this set of contacts, which is provided for a. purpose to he hereinafter described. Therefore, assuming; that connection is desired with mg station 42 which station is represented at tl'u-x'central 'ollice by multiple jacks 63,63 etc, ar. switch contacts 85 86" 87 88 and act than whenthe wipers of the switch are stopped to the 'set of contacts 85 86 etc. lilrewiscgto the set-of contacts 85 86 ground will be encountered on the con- 88 and 88 ofthese sets, and the switch will he moved in each case. to the next ion, or finally to the contacts 85 86, v which represent the line with which we have assumed a connection is desired. Contact 88 of thisgroup will be disconnected from ground, inasmuch as relay 61 is energised through the presence of a plug in the no is itchln'iard jack 68, relay 62 not as yet be inn; energized, and consequently-the wipers ll,' etc, will remain on the switch conta ts associated with this line. As previly described, stepping magnet 10" is made Lite sinuiltaneously with the operation 55m ipiiiig magnet 10 'l.herefore, the oil the sub-ollicc end of the trunk 2. will hare been mored to the contacts Q etc or in OllllGFWVOl'ClS, to the racts oi the line of station l2. station of this line is not. engaged in originating calling; the slow-acting rewhic have been i'naintaining the ciridi ions since the initial impulse. will dei nrgiucd and tlll:.\\'l1j)ll'S oi the ated with this trunk will re 'et of sub'oflice switch (.Ol'ltuCti-l. l9 will, througgjh'its upper set of coni establish a circuit through the wi 'mr tor the operation of relay 6'3. hereby disconnecting the common starting wire 514 from this line. Through one of the lower of cinitacts of relay l gzjrouiul will be placed on the wiper 4 and contact 'l'or 'M the pua' iose of causing wipers of other so .tches to pass over the multiple contacts of this line 'lfhrough the other lower set ol: a of this relay a circuit is established n' i will ultimately serve a portion oi the re 1e circuit when relay ('31. 1S deenerglzed on the removal of the plug from the'switch board acli'. The deenergization of relay l8 coiniects the line contacts 85 and Flt-l, tlirsrigh the wipers 1 and 2", to the trunk conductors are an ll-3 respectively, thereby priafluiiiiiirg a circuit over which conversation L place andover which ringing and .isory annals may be passed. The Q wire a which as before described. is group of lines. is connected through contacts of the olii'-nornial switch and contacts of the relay 18 to wire 52 assol t livitli another switchserving the same of subs At the sub-office the etion of "the relay 18 connects the ator may ring the subscriber in the subs'crilmrs line with the windings of re pcating coil 68 through the wipers l. and 2 and switch contacts 80 and S1 respectively. This relay also provides a path for the operation of cut-oil relay 5%. lelay 67 is now dcenergized and connects battery through the superrism'y rclav to one winding: of the repeating? coil 68". The corresponding winding oi the repeating coil (38" alr ady connected through the resistance 56" to ground, so that this deii nergizing of the relay 67 results in estalilisliiun a complete superrisory and talking circuit for the subscrihcus station. The suliiscriber s line is now connected through repeating coils to its associated central oiiice jack, and the operusual manner.

The cord circuit, shown in Fig. (l, is of the. type in which a. battery, through resistance is connected to the sleeve of the plug during the ringing period, thereby insuring that relay 1 and trunk release relay E will remain energized. Relay (37 at the SH!)- ollice end ol the trunk is of a type which will readily respond to ringing: current and will thcrelrv connect the trunlc conductor l3 through the switch apparatus to the limb &5?" of the subscribers line. therein eliminaliug the necessity of ringing through the repeating; coil. This circuit oi my iurmition is adapted to provide the customary signaling or supervisory means between the sul. srribcus ition and the central ollice in a. uuunu-r similar to that pro'rullal in, the circuit shown in 1 in. ll. and therefore in ol' the previous drscription, will be reaiilily umlerslood from the drawing. The means for insuring the continued cncrgimtiou ol' the release relay 20 is also ;:I:nilar to that illl.'(?zl(l described.

lt "was assumed that the station with which connection was desired was not cncaged in an. originating call. ll this station had been so engaged, PE'LWlHlOllS are made for notif ing the operator of that fact. lt will be remembered that in connection with Fig. 3 a ground connection was placed on switch contact 1 when that line was connected with the central oilice. These contacts, as well as all the contacts of a set, are multipliedthrough the S\\'lt(lli(35 associatiial with lmth incoming and outgoing trunks, serving the samegroup of subscrih= ors at the suh-olli'ce. Therefore, when the line is busy in connection with an origir'umtinn call, this corresponding contact in each of the switches is connected to ground. Consequently, when a. switch at the SlllJ-O'll'lCO minted with an outgoing trlilnlc rem the main ollice attempts to connect with a busy line, ground is connected to the Wiper l", and through the. contacts of the cut-oil relay 18 a circuit is established which causes the energization of the release relay 12, thereby memes restoring the wipers otthis switch to their normal position. When the oil-normal switch changes the relation of its contacts.

which occurs as the wipers return to normal position, a circuit is provided from battery. through'the winding ot the stepping magnet' 10 contacts 36 and 37 of the offno'rmal switch, winding of repeating coil '68, conductor -i contacts of relay 18 wiper l switch contact 85 to tip of multiple jack -83, tip'of plug 57 thence to ground through the supervisory relay 58 This circuit will cause stepping magnet to move the wipers from their normal position to the contacts 80 81 etc, and as the circuit which caused this movement will then thenotification of the busy condition, will restore the apparatus to normal as hereinafter described.

The release of the trunk line and its associated switches at the end of the conversation, or when connection is no longer wanted between the main oiiice and the sub-oflice terminals of the subscribers line, is controlled by the operator, and is accomplished by the withdrawal of the calling plug from the multiple jack. The main office switch is restored first, and when this switch is at its normal position the switch at the subofiice is restored. Certain preliminary release circuits, as heretofore described, have been established. When the operator removes the plugfrom jack 63, relay 61 is deenergized and ground is placed on the switch contact 89 The ground completes the circuit through contacts of the relay 19 and the off-normal switch thus opera-ting relay 12 Relay 12 is of the locking type, as previously described, and will remain in an energized position until the switch wipers reach their normal contacts. The operation of relay 12 causesthe operation of relay 18 which relay continued the energization of the'trunk release relay 20 until the trunk switch at the central oilice has returned to its normal position. When relay 20 is de- I subscribers lines have. 11 5a beenphysically' contacts of the release relay 20".

dissociated and the trunk line and its associated apparatus is in its normal position.

In order to prevent a trunk line and its associated appa ratus from becoming inoperative, due to the starting of a switch by an accidental momentary operation of the armature of relay 61, provision is made for automatically releasing the switch when the wipers have passed over the switch contacts and have .failed to find a switchboard terminal with which connection is desired with its associated subscribers line. This automatic release is provided by a row of contacts 86, 87, etc., placed immediately beyond the last line contacts of the switch. The lower contact of this group 89 is con nected to ground, and when wiper 5 rests on this contact a release circuit is established similar to that heretofore described.

in Fig. 4: I show a modified form of circuit "for incoming calls to the central oilice, whereby, in addition to the saving in line" conductors, I efiect a saving in apparatus as compared with the circuit for incoming calls as shown in Fig. 3. 'In this modification, instead of representing each subscriber's line in an answering jack at the central otlice, the trunk lines themselves terminate in answering jacks, thereby elimiating the necessity of providing switches on the central office ends of the incoming trunks. All the, advantages of the other arrangement are retained except that the operator must learn the number or designation ofthe calling subscriber by inquiring instead of by a vis ual inspection when such information is'desired or necessary. In this circuit the subscribers line, line apparatus and switch terminals are similar-to those shown in-Fig. 3. The operation of the various elements of the trunk switch is also similar. The step ping magnet 10* is initially started over the starting wire 52*, its subsequent control being through the testing wiper 45*. The relays 18 and 19* are operated by the initial operation of the armature of the magnet 10*. These relays are, as before, of the slowacting type. The release relay 12 iscontrolled through the oil-normal switch and The circuits for the operation of these various relays and magnets are self-evident by} an inspection of the drawing,.in view of the description already given in connection wlth the other circuits. The central oilice apparatus is somewhat different from that employed in- Fig. 3, in that the trunk switch and its associated apparatus is omitted entirely. The answering jack is of the cutoff type, thereby making the use of a cut-0E relay unnecessary. The description of the circuit, in so-far as itidifiers from those al-' ready described, will now be glveni -The 0 'eration 'of relay-19* completes a i i ,W at p o d a n l-err g ization of the trunk release relay 20*. This circuit may be traced as follows: from. at tery to contacts of relay 19 winding of relay 20, contacts of supervisory relay to ground. When relay 18- operates it prcvides, through a lower set of contacts, acircuit which includes a winding vof supervisory relay 50*, and causes the latter to operate. The energization oi? relay 56* coinpletes a circuit for the operation of the hue relay t9" and the continued energizetion of relay 20, as follows: from ground to winding of relay illi contacts of jack 65 trunk conductor itl'ifl winding of repeating coilGS. contacts of relay 56, winding of relay 520, contacts of relay 19* to battery The operation of relay 49 causes the illumination of the line lamp 430 and provides a circuit for continuing the energization oi relay 20* after relay 19" has been released. This latter circuit is as follows: from battery to resistance 66, contacts of relay t9 contacts of jack 65, trunk conductor to, re peating coil 68*, winding of relay 20, contacts of relay 56*, repeating coil 68, trunl: conductor l6", contacts of jack winding; of relay 4:9 to ground. The operator answers the call and completes the connection in the usual manner. The cord circuit well as the supervisory and release circuits are evident from the drawing: in View of the description of the corres mnding circuits in connection with Fig. 3,

1 In the description of the circuits of my invention I hare made reference to the 11109 provided for extending the starting wire ot a switch to another switch serving the stone group of subscribers when that switch becomes engaged in a connection. This provision is for the purpose of enabling any subscriber ot a group to obtain connection as long as any trunk associated with that group is idle. I have shown in Fig. 7 a simplified circuit embodying the elements involved in the selection of a trunk switch. In order to simplify the description, I will assume that a group of ten trunk switches serve 100 sub scribers. The switch contacts of each switch will, therefore, represent 100 lines. In thodrawiug, the wire and its ten b 'anchcs represent the starting wire and the conncc tion. to each of the lines ot' the first ten subscribers of the hundred respectively. The starting wire 90* and its branches are sinir larly associated with the second set of ten lines, and the starting wire 90 is associated with the hast or tenth group (Tf ten lines. 91 reprcscins the stepping magnet and its con tacts involved in the startin circuits. 92 represents the trunk cut-oil relay and 93 represents the oft-normal. switch. These parts are similarly shown for the secoi'rd. and also the tenth switch. It will be remembered in th previmis clcscription that the star: log Wire was disconnected from the 1, ie'iytoa stepping magnet iinniedix tial impulse, by the oli'qio i at the o l-normal switch connect n to contacts ol 0 trunk i itotl r ay, w letter relay on its release serves e the so rting w. 'c to another so cuits are shown in Fig :17.

Starting wire U0 pror' initial operation ot the lnnnediatcly alter th 7 ture of this magnet wire leadin to a contact oil. thc Ell l This circuit is open at t to the encrgiraation of relay ping magnet 91. l Vhen the storipirrg not ill ceases to operate the rria i 915 is dccnergiaed and the starting wiro W is connected through contacts otthis relay to the starting wire 90% which serves the of to d is normally" to the 3h. The circir men cut- l switch w 9% ct e switch is in usc is wire hil of the jtlr readily sccn first 'roup oi ho hrst itch or that in N that p up. the starting rm to the that L wire ot hare ii :cd a: hi d opts. lllirn all. the swilclsrs a2"- ting wires sorting; all thrs; are comic l irua'clihor. and th mitt h ll)- scrihcr (.lc.--irin;r a connection will. when ne oi the runlr lions hccouirs tree haii at his disposed this truck line rotziardlc-i: (at the group in Whirl! his line is found and the group which this swit h o rmall s rvo The order in which lllt' suliiswihcrs lines are multiplied through the romarts i the trunk switches (Hill-rs in ca -l1 :N'dtli. Thi arrzo'igcnient ot' the relation of the lime-1 with respect to the multiple is tor the purpose of normally pmuiittingg' the cooocrti o to he established with the towed possible rahos lines oi the wipers of a switch. 'lhc armngrcmr-nt is that in the first switch the first too scribe-rs lines will be (winner-to t ten sets of contacts. in the shroud su'i; the second set of n :-ulr cr l he rennet ed to the r and so on the lines norrr snitch alwa :being' connc r. of ten contacts, ln car-h r; groups oi" subscribers lines arc with. the multiple switch cont lar switch will h mihored is only when all memos contacts of the switches on the two ends of a trunk line must of course be connected in the same order. I will describe in detail the arrangement of all the subscribers lines with respect to the first switch, in order to ii ustrate this point more clearly. As before stated, the first group of ten subscribers lines will 1 e connected to the first set of ten contacts. The tenth group of subscribers lines will be connected to the second set of ten. contacts; the ninth to the third; the eighth to the fourth; the seventh to the fifth; the sixth to the sixth; the fifth to the seventhi the fourth to the eighth; the third to the ninth and the second to the tenth. It is obvious that the subscribers lines may be divided into groups having a greater or less number than one hundred served by a particular group of trunks.

in the figures illustrating the circuit arrangement of my invention I have in each case shown only one trunk line, one'subscribers line and the multiple switch confor four subscribers lines. However, do not Wish to limit my invention in this respect, as it is obvious that the number of such lines may be incresed without departing from the spirit of my invention VJhile I have illustrated and described certam forms of my invention, it is understood that numerous changes may be made therein without departing from the spirit or narr ing the scope of my invention.

Hiring thus described my invention, what I claim as new and desire to secure by United States d letters Patent is:

l. in a telephone system, a t. 'o-wire trunk line adapted to form a talking circuit between two points;' two selecting switches, one for each end of said trunk line; electromagnetic means for automatically moving said switches in unison to establish a talking connection over said trunk, and means for releasing said switches, the control between said switches for both connecting and releasing being overthe two wires of said trunk. v

In atelephone system, a trunk line adapted to form alink in a talking circuit; two selecting switches, one at each end of said trunk line; means for automatically moving said two switches in unison to extend the two ends of said trunk line; and means for releasing said switches, the control between said switches for both connecting and releasing being over the talking wires of said trunk.

3. In a telephone system, a central ollicefor returning the switches to their normal positions at the end of a conversation, the control of said switches between said ofiices being over the talking wires of said trunk.

4. In a telephone system, a switchboard having a plurality of subscribers line terminals; a plurality of subscribers lines dissociated from said switchboard line termi-- nals and pertaining respectively to each of said switchboard terminals; a two-wire trunk common to all said subscribers lines; a switch for each end of said trunk; means for causing said switches automatically to connect one of said subscribers lines to its corresponding switchboard terminal when a call is initiated on said line; and means for releasing said switches, the distant cmntrol of said switches for both connecting and releasing being over the two conductors of said trunk.

5. In a telephone system, a switchboard having a plurality of subscribers line terminals; a plurality of subscribers lines dissociated from said switchboard and pertaining respectively to each of said line terminals, a two-wire trunk common to all said subscribers lines; a switch for each end of said trunk; means for causing said switches automatically to connect one of said terminals to its corresponding subscribers line when a connection is initiated with said switchboard terminal, and means for releasing said switches, the distant control of said switches for both connection and releasing being over the two conductors of said trunk.

6. In a telephone system, a group ofsubscribers lines; a switchboard having a group of line terminals normally dissociated from said lines; a trunk common to the lines and terminals of said respective groups and adapted to form a link in a talking circuit between any subscribers line and its corresponding switchboard terminal; switches at each end of said trunk acting automatioally to connect a subscribers line with its corresponding switchboard terminal upon the initiation of a call on said line, and means for releasing said switches, the distant control between said switches in connecting and releasing being over the talking conductors of said trunk.

7; n; a telephone system, a switchboard having a plurality of subscribers line terminals; a plurality of subscribers lines dissociated from said switchboard and pertaining respectively to each of said line terminals, a trunk common to said lines and terminals and adapted to form a link in a lking circuit between any subscribers line and its corresponding switchboard terminal; a switch for each end of said trunk; means for causing said switches automatically to con nect one of said terminals to it's corresponding subscribers line whena connection is initiated with said switchboard terminal;

and means for releasing said switches, the means for releasing one of said-switchesbeing controlled over one of the talking wires of said trunk.

8. In a telephone system, a switchboard having a plurality of subscribers line ter ininal-s; a plurality of subscribers lines dissoeiated from said switchboard and pertaining respectively to each of said line terminals; a trunk common to said subscribers lines and terminals and adapted to form a link in a talking circuit between any subscribers line and its correspondin terminal; a switch for each end of sai trunk; means for causing said switches automatically to connect one of said terminals to its corresponding subscribers line when an outgoing connection is initiated at said switchboard terminal; and means for releasing said switches, the means fonreleasing the switch at the subscribers line end of said trunk being controlled over "one of the talking conductors of said trunk.

9. In a telephone system, a two-wire trunk line adapted to form a link in a talking cir- (-uit; two selecting switches, one at each end of said trunk line; means controlled over one side of the talking circuit of said trunk for automatically movin said two switches in unison to extend the two ends of said. trunk line; and means for releasing said switches, the release means for one of said switches being controlled orer the other side of the talking circuit of said trunk.

10. In a telephone system, a two-wire trunk line adapted to form a link in a talking circuit; an automatic selecting switch at each end of said trunk line; a group of paths terminating in each of said switches; means for automatically moving said two switches in unison to connect the two ends of said trunk line to corresponding ones of said paths, said means being controlled. over one side of the talking circuit of said trunk, and means for restoring said switches, said restoring means being operated over the other side of the talking circuit of said trunk.

11. In. a telephone system, a central office and a sub-office; a group of subscribers lines terminating at said sub-oilice; a trunk common to said group of subscribers lines adapted to form a talking circuit between said oilices; a switch for said trunk at said sub-oiiice adapted to automatically establish a connection between one of said lines and said trunk upon the initiation of a call on said line; and means for releasing the switch ofsaid trunk, said means being controlled over-one of the talking wires of said trunk.

12. In a telephone system. a switchboard having a plurality of subscril' ers line equipments; a plurality of subscribers lines dissociated from said switchboard and pertainin; one to ea h of said line equipments; an

automatic switch for selecting and connect ing with said subscribers lines; an automatic switch for selecting and connecting With said subscribers line equipments of said switchboard; a two-wire trunk line connecting said switches; means controlled over said trunkline for causing said two automatic switches to move in corresponding steps during selection; and means for restoring said two automatic switches, the restoration of one of said switches being controlled over one of the two wires-of said trunk line. 13. In a telephone system,a*-eentral ofiice and a sub-office; a group of; subscriberslins terminating at said sub-oilice; a switchboard having a plurality of subscribers line' terminals at said central ofiice; a plurality of trunk lines, less in number than the subscribers lines or corresponding switchboard terminals, said trunk lines being adapted to form cdnnectinglinks in the talking circuits between the subscribers lines and the central ofiice; a selecting switch at caclrencl. of each trunk line; means for appropriating an idle one of said trunk lines upon the initiation of a call on a subscribers line; means for causing the switches of-the trunk line so appropriated to connect at one end with the subscribers line and at the other end with the corresponding switchboard terminal; and means for causing the release of said switches, the control between said switches for both selecting and releasing being over the talking circuit wires oi said trunk line. 1

'14. In a telephone system, a central office and a sub-office; a group of subscribers lines terminating at said sub-ofiice; a switchboard having a plurality of subscribers line terminals at said central ofiice; a plurality of trunk lines, less in numberthan the subscribers lines or correspondingswitchboard terminals, said trunk lines bein adapted to form connecting links in the tal 'ng circuits between the subscribers lines and the central ofiice; a selecting switch at each end of each trunk line; means for appropriating an idle sub-office being controlled over one of the talking conductors of said trunk.

15. In a telephone system, a central ofiice and a sub-office; a group of subscribers lines terminating at said' sub-office; a switchboard having a plurality of subscribers line ter-; minals at said central office; a plurality of trunk lines, less in number than the subscribers lines or corresponding switchboard menace terminals, said trunk lines being adapted to form connecting links in the talking cir cults hetweenthe subscribers lines and the central oilice, a selecting switch at eachend of each trunk line means for appropriating to connect respectively at one end with the switchboard terminal so connected with, and at the other {end with the corresponding subscribers line; and means for causing the release of said switches, the control between said switches forboth selecting and releasing being over the talking circuit wires of said trunk linew I ltilna telephone system, a central oliice and a sub-oilice; a group of subscribers lines terminating at said sub-oiiice; a switchboard having a plurality of subscribers line terminals at said central oiiice; a plurality of trunk lines, less in number than the subscribers lines or corresponding switchboard terminals, said trunk lines being adapted to form connecting links in the talking circuits between the subscribers lines and the central oflicega selecting switch at each endof each trunk line; means for appropriating an idle one of said trunk lines upon the establishment or? an outgoing connection with a switchboard terminal at the central ofiice; means for causing the simultaneous operation of the two switches of said trunk to connect respectively at one end with the switchboard terminal so connected with, and

at the other end with the corresponding subscribers line; and means ior causing the release of said switches at the end of a conversation, the release of the switch at the sub-office being controlled'over one of the talking conductors of said trunk.

17 In a telephone system, a central ofiice and a sub-oilice; a group of subscribers linesfw terminating at said sub-oliice; a group of f trunks common to said group of subscribers!- lines,'but less in numberthan said subscrib ers lines extending between said oflices; a

switch for each of said trunks at said suboffice; means for appropriating an idle one of saidtrunk lines upon the initiation of a 7 call on one ofsaid lines; means for causing the operation of the switch of an appropriated trunk to connect said trunk with said line, and means for releasing the switch of said trunk, said latter means'being C011. trolled at said central 0fii 3e over one of the talking wires of said trunk.

18. In a telephone system, a central ofiice so and a sub-olilce; a group of subscribers lines terminating at said sub-oilice; a group of two-wire trunks common to said group of subscribers lines, but less in number than said subscribers lines extending between said ofiices; a switch for each of said trunks at said sub-oilice; means for appropriating an idle one of said trunk lines upon the initiation of a call on one of said lines; means for causing the operation of said switch of "10 an appropriated trunk to connect said trunk with said'line, and a release relay at said sub-ofilce, said relay being controlled over one of the wires of said trunk.

Signed by me at Chicago, county of Cook and State of Illinois, in the presence of two witnesses.

EDGAR I-I. CLARK. 

